Protecting an icemaker against overcurrent damage

Abstract

A wound bobbin coil (A) and a fuse (B) are interconnected electrically in series. The coil and the fuse are mounted closely adjacent and molded into a tough, nylon encapsulation (C). The series connected coil and fuse are connected with electrical terminals (26, 30) to form a unitary electrical component which is readily connected with associated circuitry. In this manner, when the coil becomes damaged sufficiently to blow the fuse, both the coil and the fuse must be replaced. A repairman cannot short the fuse or merely replace the fuse and allows a damaged coil to continue functioning. In the preferred utilization of the present coil in a freezer compartment ice maker, coil failures can cause flooding, overheating, and other catastrophic damage to a refrigerator/freezer.

Having thus described the preferred embodiment, the invention is now claimed to be: 
     
       1. An assembly for a refrigerator icemaker comprising: (a) an electrically operated coil adapted for actuation of an electromagnetic water fill valve upon normal operating current flow, said coil having a plurality of turns therethrough of relatively fine wire having the size chosen such that upon flow of normal operating current therethrough a desired magnetomotive force is produced and upon flow of said normal operating current in excess of a predetermined time, said coil being heating and undergoes successive shorting of windings thereby decreasing the electrical resistance of said coil and increasing current flow therein, said coil operative upon said decreasing resistance for de-actuating a water fill valve   (b) heater means electrically series connected with said coil and operative for heating ice for removal from a tray, said heater means having a greater resistance then said coil and acting as a voltage divider and a current limiter to prevent coil burnout despite said shorting; and,   (c) circuit protective means series connected to said heater means and operative upon said coil decreasing resistance for terminating current flow through said heater means.   
     
     
       2. A control system for a refrigerator icemaker comprising: (a) an electrically operated coil adapted for actuation of an electromagnetically actuated coil for controlling ice maker waterfill, said coil having a known impedance and defining an armature receiving cavity and having a plurality of turns of relatively fine wire chosen such that the turns increase in temperature and successively short out in the event a normal operating current continues to flow for a time greater than a predetermined normal waterfill cycle time, said shorted coils operative to decrease the impedance of said coil and the magnetomotive force sufficient to cause said valve to be electromagnetically deactuated and operative to permit current greater than a normal operating current to flow therethrough;   (b) heater means electrically series connected with said coil and operative to perform an ice melting function upon flow of a normal operating current therethrough, said heater means operative as a voltage divider with said coil having an impedance higher than said coil such that said heater acts as a current limiter for said coil and said coil upon said coil shorting continues flow of greater than normal current and is prevented from overheating and acting as a fuse;   (c) current terminating means electrically series connected with said heater means, said terminating means operative to create an open circuit only when a predetermined limit current above normal operating current flows in said heater means; and,   (d) controller means, operative to effect switching of current to said coil for normal ice maker waterfill.   
     
     
       3. The assembly defined in claim 2, wherein said coil and current terminating means are commonly encapsulated with plastic material. 
     
     
       4. An appliance control system comprising: (a) a solenoid coil having an impedance and defining an armature receiving cavity and having a plurality of turns of relatively fine wire chosen such that, upon flow of a normal operating current therethrough a magnetomotive force is provided sufficient for effecting a first operating function, said coil turns, upon said normal current flowing continuously beyond a predetermined threshold interval of time, subject to shorting out of successive turns, whereupon said coil impedance drops and said coil becomes inoperative to effect said first appliance function;   (b) heater means electrically series connected with said coil and, upon flow of said normal operating current therethrough for a time interval less than said threshold, said heater means operative to effect a second appliance function, said heater means and said coil forming a voltage divider whereby when said coil impedance drops current through said heater continues and increases to a greater than normal level;   (c) fusing means electrically series connected with said heater means and coil and operative to maintain current in said heater means as said coil impedance drops and to go open circuit only when the current in said heater means reaches an unacceptable level; and,   (d) controller means connected in circuit with said coil, said heater means and said fusing means, said controller means operative to switch power to said heater means, coil and fusing means in a predetermined program for effecting said first and second appliance functions.   
     
     
       5. The control system defined in claim 4, wherein said coil and fusing means are encapsulated commonly in plastic material. 
     
     
       6. The assembly defined in claim 4, wherein said coil is encapsulated in plastic material and includes a pair of electrical connection terminals extending from the plastic encapsulation for interconnection with an electrical socket, the electrical terminals being connected in series with the coil and the current terminating means. 
     
     
       7. The assembly defined in claim 4, wherein said coil and fusing means are encapsulated commonly in plastic material and said fusing means includes a shell defining an air space therein and a fuse element extending through its shell air space.